Silt removal

ABSTRACT

POLYMERS OF CERTAIN N-(ALKYL) AMINO ACRYLAMIDES ARE USEFUL TO REMOVE AND PREVENT SILT ACCUMULATIONS IN WATER SYSTEMS, SUCH AS COOLING SYSTEMS AND THE LIKE. THE PREFERRED MONOMER IS (3-ACRYLAMIDO-3-METHYL) BUTYL TRIMETHYL AMMONIUM CHLORIDE; THIS MONOMER MAY BE HOMOPOLYMERIZED OR PRESENT TO THE EXTENT OF AT LEAST 1 PERCENT IN A WATER-SOLUBLE POLYMER OF AT LEAST 100,000 MOLECULAR WEIGHT.

Unit s ate P te ,0 73cc a Patented Aug. 14,

a i i 2 mfi'i riglflt '23, 3752760 SILTREll IOVAL s N 1k A K x Robert Cornelius Gordon, Jr., Rochester, Jerry Lee 7 t a R2 Walker, Coraopolis, Andrew Jackson Sharpe, Jr., Mc- I i v 7 and Jen-y Emile Boothe, Pittsburgh, Pa m WhlCh R and R are independently selected from siguors to Calgon Corporation, Pittsburgh, Pa. linear and branched alkyl groups having P to 18 carbon No Drawing. Filed Mar. 9, 1972, Ser. No. 233,322 atoms, aralkyl groups having up to carbon atoms, and Int. Cl. C02b 5/06 in which R and R may be combined to form a hetero- 210-58 3 Clalms 10 cyclic group having one or more hetero atoms; R3 is v selected from the group of-hydrogen, lower alk l rou s .ABSTRACT OF THE DISCLQSURE of 1 to 4 carbon atoms-and halogen; R is selec te fro zn Polymers of certain N-(alkyl) amino acrylamides are the group of hydrogen, o a lineal a e alkyl useful to remove and prevent silt accumulations in water group of P to 5 carbon atoms; 5 is P y lower'alkyl systems, such as cooling systemsand the like. The preto 4 carbon Substituted P y wherein the ferred monomer is (3-acrylamido-3-methyl) butyl tri- Substituellts y be lower alkyl 0 4- t n methyl ammonium chloride; this monomer may be homolower alkOXy t0 4 carbon s 4 can polymerized or present to the extent of at least 1 percent Combine With 5 to form a eyelic group of at vleaet in a water-soluble polymer of at least 100,000 molecular carbon atoms or a bieyelie group -le 7 ar n i ht, 1 atoms, which groups can be substituted with a linear or Y branched alkyl group having up to 5 carbon atoms; R BACKGROU O T INVENTION is selected from hydrogen and methyl; R may be any a group capable of quaternizing the nitrogen, including Much of the water which is used in industrial cooling the g P consisting of hydrogen, yL p y s systems, such as for example, the cooling systems in blast y yl, and linear, branched and Substituted alkyl furnaces, open hearth furnaces and the like in the steel d aralkyl groups having 1 to 16 carbon atoms, the industry, and cooling towers in the oil industry, is de- Substitutions therefor being halide, and rived from rivers, ponds, lakes or other sources of im- -SO Where the counter ion for the anionic substipure natural waters. These natural waters carry various Union is normally hydrogen alkali metal; X y be amounts of silt, mud, and/or Organic wastes and other any anion, preferably halide, alkosulfate, tosylate, caraccumulations which deposit on heat exchange surfaces boxylate, sulfonate, sulfate, phosphate, acetate, or nitrate; and create problems of corrosion, loss of heat transfer and n is an integer from 0 to 2. efficiency, and the like, as well as reducing the area of The monomer may be copolymerized with any copothe passageways and thus the amount of cooling water lymerizable water-soluble monomer. Among the copolymwhich can be circulated. In installations, such as in the eriza'ble monomers useful in our invention are acrylic surface condensers associated with turbine generators, alacid, methacrylic acid, the alkali metal, amine and amluvium very seriously alfects the rate of energy convermonium salts of acrylic and methacrylic acids, methsion. In other areas, such as in pipes, sewers, heated water acrylamide, B-aminoethyl acrylate, 18-aminoethyl methlines, etc., the alluvium tends to block the passage of acrylate, N-methyl-p-aminoethyl acrylate, N-methyl Water, creating serious problems in water flow. 40 aminoethyl methacrylate, N,N-dimethyl p-aminoethyl In many industrial heat exchange installations and in methacrylate, and the water-soluble N-alkyl substituted many pipe line systems carrying natural waters, operations acrylamide and methacrylamides such as N-isopropyl must be halted periodically so that the system can be acrylamide. Still other comonomers of the water-soluble cleaned out mechanically or with acid or some other class are the alkali metal styrene sulfonates, and alkali means. This is obviously an expensive and highly undemetal vinylbenzoates. Also useful are allyl alcohol, N-

sirable situation. vinyl pyridine, N-vinyl pyrrolidone, and N-vinyl-Z-oxa- Various attempts have been made in the past to conzolidone. r trol and/or remove silt deposits from water systems Water-insoluble monomers may also be employed in through the use of water-soluble polymers. For example, the copolymers so long as the copolymers are soluble in see Zimmie et al. US. Pat. 3,085,916, wherein polyacryl- Water to the extent of 0.05 percent. Suitable monomers amide is employed, Flock US. Pat. 3,288,640, which disare styrene, methylacrylate, acrylonitrile, butadiene, and closes the use of'polyethyleneim'ine, and Zierden U.S. methyl methacrylate. All polymers andcopolymers should Pat. 3,503,879, which uses high molecular weight potashave molecular weights of at least 100,000.

sium metaphosphate. We are also aware of the use of Preferred copolymers are copolymers of (3-acrylamido- N-sulfohydrocarbon-substituted acrylamides for this pur- 3-methyl) butyl trimethyl ammonium chloride pose. See Canadian Pat. 864,433 for a description of the (AMBTAC) polymer. 7

The use of such polyelectrolytes as described above and acrylamide We Prefer to use p y having from has certain limitations, however. Their function and efiiabout 1 100 Peleellt P y AMBTAC and 0 to 99 D ciency appears to vary from day to day and from'plant cent acrylamide, and more p y 9 Percent to plant. Since'the composition of water and the silt-like acrylamide and 10 to 30 P e AMBTAC- The y substances therein is infinitely variable, it has been very amide Portion of the P y y be y l diificult to predict the success of a given treatment on a to the extent of P to mole PeI'CeIIt of the avalleble given day. I acrylamide.

We believe the strongly cationic nature of the polymer 5 Whlle We 0 no WISh to be bound by any theories, 1t herein proposed contributes significantly to the success of pp that the Compounds 0f 1' lnventlon remove our i nti alluvial deposits from surfaces by dispersing the deposits into the water stream and agglomerating the'deposits into SUMMARY OF THE INVENTION a mobile floc which can be carried away from the surfaces Our invention contemplates the use of water-soluble 70 by the water stream. Several laboratory experiments depolymers including at least 1 percent by weight monomers scribed herein illustrate this dispersing and fiocculating of the formula effect.

' We have found that a' polymer or copolymers ability to' remove and prevent 'silt accumulation in water systems can be predicted from the polymer or copolymers ability to flocculate suspended silt deposits taken from such systems.

Some silt deposits are best removed or prevented by a strongly anionic polymer, while others are best removed or prevented by the most strongly cationic polymers. In addition, certain types of silt deposits are best controlled through the use of-a nonionic polymer or copolymer. Although chemical analyses of these silt deposits often reveals only slight differences, we have been able to develop two synthetic, silts, oneof which is typical of those silt'deposits controllable by an anionic polymer or copolymer and one ofwhich is controllable by a cationic polymer.

Compositions of the synthetic silts are as follows.

7 TABLE 1 Synthetic silt composition for anionic polymers Material:

For cationic polymers, the composition is 97 percent by weight finely divided SiO 1 percent hectorite, and 2 percent of the anionic synthetic silt composition shown in Table l.

Surprisingly, excellent flocculation of both of these synthetic silts was obtained by use of the polymers and copolymers of this invention. In the case of the synthetic silt typical of those field or industrial silts best controlled by an anionic polymer, 2.5 grams of the synthetic silt was added to 250 milliliters distilled water in a 250 milliliters graduate cylinder. The cylinder was then inverted five times and the time required for the silt to settle to a total accumulation (height) of 110 milliliters was recorded. The polymer or copolymer was then added to a concentration of 0.4 p.p.m. and the graduate again inverted five times and the time in seconds to settle to an accumulation of 10 milliliters was recorded. 'These results are shown in Table 2.

TABLE 2 Polymer (weight ratios): Time/10 milliliters, seconds 80 AM/ 20 AMBTAC 25 50/50 25 20/80 I 30 0/100 (homopolymer) 35 In addition, a silt deposit collected from a midwest paper'm'ills surface condenser was evaluated in the normal manner. The relative elfectiveness of various polymers and copolymers to fiocculate this field (industrial) silt deposit sample is shown in Table 4, with the most effective being rated as number 1 and the least effective as number 4.

Acrylamide/Z-acrylamide propyl sulfonic acid copolymer (anionic, 49 AM/Sl 2-AMPSA, acrylamide hydrolyzed 50 percent) 4 Hydrolyzed polyacrylamide (35 percent hydrolyzed 4 r The dimethyl diallyl ammonium chloride homopolymer and polyethyleneimlne homopolymer were about equal, but considerably less etfective than AMBTAC The AM/2-AMPSA and hydrolyzed polyaerylamtde showed no significant difierences during test period.

Preferably we add to the water system and/or maintain in a water system at least about 0.05 ppm. of the desired polymer in order to prevent deposits from forming. Of course, greater concentrations may be necessary initially and for a period of time theerafter to clean a system which is already laden with deposits. Large con- 49 AM/SlAMPSA (partially hydrolyzed) 23 Control (no treatment) 180 On the other hand, the synthetic silt typical of those field silts best controlled by cationic polymers or copolymers gave the results as shown in Table 3 when treated with 1 p.p.m. of the polymers or copolymers of this invention. I

Control (no treatment) e 200 centrations may be added or maintained in a water system without apparent ill effect, but it is uneconomical and wasteful to maintain concentrations in excess of about 30 p.p.m. The system is preferably periodically flushed out.

A satisfactory and often more economical alternative method of practicing our invention is to periodically add to the water in the system relatively higher concentrations of the compounds of our invention for a short period of time. In this embodiment of our invention, we prefer to maintain concentrations of at least about 1 p.p.m. based on mass flow of water in the system, for periods usually of about 30 minutes to 2 hours, at least about once a week, although the interval between such periods of addition may range from about 4 hours;to about 7 days or more. Aninterval should be chosen for each system which will maintain the heat exchange efliciency of the system continuously at a high level.

' We claim:

1. Method of: controlling the deposition of alluvium and silt in a water system comprising adding to said system at least. 0.05 p.p.m. of a water-soluble polymer containing at least 1 percent by weight of a cationic monomer of the formula inwhich R and R 2 are independently selected from linear and branched alkyl groups having up to 18 carbon atoms, aralkyl groups having up to 10 carbon atoms, and in which R and R may be combined to form a heterocyclic group having one or more hetero atoms; R is selected from the group of hydrogen, lower alkyl groups of 1 to 4 carbon atoms and halogen; R is selected from the group of hydrogen, halogen, a linear or branched alkyl group of up to 5 carbon atoms; R is phenyl, lower alkyl (1 to 4 carbon atoms), substituted phenyl wherein thesubstituents may be lower alkyl (1 to 4 carbon atoms), or lower alkoxy (l to 4 carbon atoms); R or R can combine with R to form a cyclic group of at least 6 carbon atoms or a bicyclic group of at least 7 carbon atoms, which groups can be substituted with a linear or branched alkyl group having up to 5 carbon atoms; R is selected from hydrogen andmethyl; R may be any group capable of quaternizing the nitrogen, including the group consisting of hydrogen, benzyl, phenethyl, cyanoethyl, and linear, branched and substituted alkyl and aralkyl groups having 1 to 16 carbonatoms, the substitutions therefor being halide, -OH, COO-, and SO wherein the counter ion for the anionic substitution is normally hydrogen or alkali metal; X may be any anion, preferably halide, alkosulfate, tosylate, carboxylate, sulfonate, sulfate, phosphate, acetate, or nitrate; and n is an integer from to 2.

2. Method of claim 1 n which the cationic polymer contains at least 1 percent by weight (3-acrylarnido-3- methyl)buty1 trimethyl ammonium chloride.

3- Method of claim 1 in which the polymer is a homopolymer of (3-acrylamido-3-methyl)butyl trimethyl ammonium chloride.

4. Method of claim 1 in which the polymer is at least 0.05 percent soluble in water.

5. Method of claim 2 in which the polymer is a copolymer of (3-acrylamido-3-methyl)butyl trimethyl ammonium chloride and acrylamide.

6. Method of controlling the deposition of alluvium and silt in a water system comprising adding and maintaining therein at least about 0.05 p.p.m. of a copolymer of to 99 percent acrylamide and a 1 to 30 percent (3-acrylamido-3-methyl) butyl trimethyl ammonium chloride.

7. Method of claim 6 in which the acrylamide portion of the polymer is at least partially hydrolyzed.

8. Method of claim 1 including the step of flushing out of the system the alluvial particles agglomerated by the polymer.

References Cited UNITED STATES PATENTS 3,472,767 10/1969 Lees 2l0'54 X 3,579,445 5/1971 Tate 21058 3,692,673 9/1972 Hoke 2l052 MICHAEL ROGERS, Primary Examiner US. Cl. X.R. 

